Abstract. Identifying specific causes of reduced EC NO generation in the context of aging is a high priority so that mechanistic insights can be gained for the development of new therapeutic targets for intervention. Autophagy is compromised in arteries from old vs. young mice, but the contribution from EC autophagy per se to arterial function is unknown. Our experiments will elucidate the contribution of impaired EC autophagy to vascular dysfunction. Autophagy is a conserved process whereby cells respond to nutrient and environmental stress. Healthy aging is a complex cellular stress. Autophagy is repressed in individuals with age-related neurodegenerative diseases. These findings have stimulated research to determine whether impaired vascular autophagy impairs EC NO synthesis and/or exaggerates NO destruction. The Seals laboratory group has shown proof of concept that EC autophagy per se might regulate NO synthesis to an extent that is functionally relevant. We have shown that silencing Atg3 or Atg5 expression impaired shear-stress induced autophagy as expected, but prevented shear-induced eNOS phosphorylation and NO generation, and amplified indices of inflammation and adhesion. Neither method of autophagy suppression evoked cell death or apoptosis. Collectively, compelling evidence suggests impaired EC autophagy compromises EC NO bioavailability. It is unknown whether disruption of proteins requisite for autophagy in ECs impairs vascular function in vivo or ex vivo, and it is unknown whether the aging-related reduction in vascular autophagy is secondary to impaired autophagosome formation and trafficking to the lysosome or is secondary to lysosomal dysfunction. Our overall aim is to determine the contribution of impaired EC autophagy per se to vascular dysfunction using our model of inducible Atg3 knockdown in ECs. Three experiments will address the following questions: (A) Can the aging-induced reduction in vascular function be recapitulated in young iecAtg3KO mice?; (B) Can the aging-induced disruption of vascular eNOS enzyme function, NO bioavailability, and redox balance be recapitulated in young iecAtg3KO mice?; and (C) Does aging dysregulate autophagosomal initiation or autophagosomal degradation? Further, because our preliminary findings in several models of autophagy suppression clearly demonstrate activation of p53, we will (D) test the hypothesis that posttranslational modification of p53 via MAPK in the context of autophagy suppression disrupts the interaction between murine double minute 2 (Mdm2) and p53, ultimately activating this known feature of vascular aging. Results from these experiments will provide the requisite preliminary data from which to craft a series of future investigations designed to elucidate the mechanistic link(s) between compromised EC autophagy and impaired NO generation / increased NO destruction. Once the link(s) between impaired autophagy and reduced NO bioavailability has been discerned, targeted ?rescue? experiments can be designed and tested in aged mice using novel gain-of-function procedures.